Ok...

Unpopular opinion but I think they needed to separate on that island. I think people keep forgetting how large his father's influence is. He sent that bum after them and he found them easily! They would HAVE to be on the run together and ultimately that would put a tremendous strain on their relationship. His dad would never stop until Duk was arrested just to get to Sungho. Sungho is just now getting to a point where he can stand up to his father and not to spoil too much, but he's still not quite there yet. That took 8 years. Let the man cook! So yeah, just wanted to get that off my chest. Sungho has a lot of flaws as a character, but this was a decision that I honestly don't blame him for.